Best place for body parts for 1975 XJC

You could always try Wolf panels.
http://www.alfaparts.net/xjc.htm

ManShun Poon

2001 Jaguar XJR
1987 Jaguar V12 VDP
1986 Jaguar XJ6

Pauls Jags in Florida used to specialise in XJC's. Don't know if he still does. E-mail is paulsjagaol.com. Might be worth dropping him a line to find out.

Bob.
92 Ser III V-12 VDP #31 Canadian Edition
87 Ser III V-12 VDP
86 Ser III AJ6/Soveriegn

there's no best place for that model, (or any other Jaguar model for that matter!), but for the XJ-C there are bits and pieces sold by a good number of different businesses, mostly in the UK or Australia, each having a few parts here, a few parts there. In the US you will find mostly used parts or parts cars, though there are a few selling some reproduction parts.
I hope this helps some.